Been shooting my 6.5 Grendel bolt rifle a lot here lately and using a ball powder that has a copper preventer in it, kinda dirty. So every time I get ready to tumble my brass I'm cleaning the carbon/soot of the necks with a piece of scotch-brite pad. Today at the range a old timer showed me a solution and it blew me away it was so simple. He pulled out a towel from a can of "Tub-o-towels" and cut me off a small piece and said "wipe the necks off as soon as the come out" and this works! perfectly clean necks.